1. Field of the Invention
The present invention relates to a necrotic cell region detection apparatus and a method of the same to detect a region formed by necrotic cells from a cell image acquired by imaging using, for example, a bright field microscope, and a non-transitory computer readable storage medium to store a necrotic cell region detection program.
2. Description of the Related Art
Heretofore, in medical and life-science fields, various cell analyses using a cell image photographed through a microscope have been conducted. For example, in the studies of stem cells such as ES cells and iPS cells, the following operation is generally performed for the elucidation of cell differentiation mechanisms and the discovery and development of drugs: cell differentiation processes and morphological feature changes are observed from cell images obtained in a time-series manner, and the difference of characteristics of cells is investigated.
Regarding the analysis of the cell image, automation of troublesome operations such as the screening of individual cells that has heretofore been visually performed is becoming possible by the application of image processing technology such as image recognition. If this image processing technology is applied, it is possible to measure the degree of activity of individual cells included in the cell image by calculating the contours of the cells and detecting morphological information regarding the cells and the number of cells or the motions and movement distances of the cells.
The activities of cells are balanced by the mechanism of cell death called apoptosis (natural death) and necrosis as well as by cell proliferation resulting from cell division.
In apoptosis, a change is first made in the cell nucleus, and the cell decreases in size, forms an apoptotic body, and is then engulfed by immunocytes or the like and digested without any trace left. Meanwhile, in necrosis, the whole cell gradually inflates, the cytoplasm changes, and then the cell membrane finally bursts. At the same time, the contents of the cell remain, and cause inflammation (cytolysis).
The region in which the cell contents remain due to necrosis (hereinafter referred to as a necrotic region) is difficult to distinguish from a living cell region when individual cells are extracted in cell detection, which is likely to have an adverse effect on, for example, correct measurement of the number of cells, or evaluation of the degree of cell activity by the measurement of the number of cells. Therefore, it is necessary to correctly recognize the necrotic region in advance.
Jpn. Pat. Appln. KOKAI Publication No. 2007-20449 discloses a method intended for drug screening to judge whether a cell is a living cell or a dead cell on the basis of a morphological feature value representing the morphological feature of each cell in a cell image acquired by a microscope. More specifically, according to Jpn. Pat. Appln. KOKAI Publication No. 2007-20449, the judgment is made by the use of the amount of deviation of the contour shape of a cell from a circle or a sphere as the morphological feature value representing the morphology of the cell. A cell judged to be large in deviation amount is considered to have been significantly distorted from a circle or sphere, and is judged to be an active living cell. In contrast, a cell which is small in deviation amount and which is close to a circle or sphere is judged to be inactive and nearly dead.